1. Field of the Invention
The present invention relates to a method of manufacturing racks for variable ratio rack and pinion steering gears.
2. Description of the Prior Art
A rack for such a variable ratio steering gear has teeth that may vary in pitch and shape to provide a variable steering ratio, as described in U.S. patent application Ser. No. 297,932 and No. 312,137, both assigned to the same assignee as this application. This kind of rack is manufactured by a method of including a preforming process for preparing a rack blank having teeth which are formed to a shape closely approximating the shape desired in the finished rack and a finishing process for converting the teeth to the finished shape by cold forming or coining in a die having a shape which is the exact counterpart of the finished shape, as described in U.K. patent application No. 2,026,908 and U.S. Pat. No. 4,193,722.
This prior art method is plagued by a problem that the quality of the product tends to vary widely, leading to difficulty in maintaining a desired level of quality. The method is faces another problem that the die for the finishing process tends to be damaged in a short period of use.